Blocky mountains. Mountains: characteristics and types Blocky mountains 1 3 on the map
Mountains can be classified according to different criteria: 1) geographic location and age, taking into account their morphology; 2) structural features, taking into account the geological structure. In the first case, mountains are subdivided into cordillera, mountain systems, ranges, groups, chains and single mountains.
The name "cordillera" comes from the Spanish word meaning "chain" or "rope". The cordillera includes ranges, groups of mountains and mountain systems of different ages. Cordillera region in the west North America includes the Coast Ranges, the Cascade Mountains, the Sierra Nevada, the Rocky Mountains, and many smaller ranges between the Rocky Mountains and the Sierra Nevada in Utah and Nevada. The Cordilleras of Central Asia include, for example, the Himalayas, the Kunlun and the Tien Shan.
Mountain systems consist of ranges and groups of mountains that are similar in age and origin (for example, the Appalachians). The ranges consist of mountains stretched out in a long narrow strip. The Sangre de Cristo Mountains, stretching in the states of Colorado and New Mexico for 240 km, usually no more than 24 km wide, with many peaks reaching a height of 4000–4300 m, are a typical ridge. The group consists of genetically closely related mountains in the absence of a clearly defined linear structure characteristic of the ridge. Mount Henry in Utah and Bear Po in Montana are typical examples of mountain groups. In many parts of the world there are solitary mountains, usually of volcanic origin. Such, for example, are Mount Hood in Oregon and Rainier in Washington, which are volcanic cones.
The second classification of mountains is based on the endogenous processes of relief formation. Volcanic mountains are formed by the accumulation of masses of igneous rocks during volcanic eruptions. Mountains can also arise as a result of the uneven development of erosion-denudation processes within a vast territory that has experienced tectonic uplift. Mountains can also be formed directly as a result of tectonic movements themselves, for example, during arched uplifts of sections of the earth's surface, with disjunctive dislocations of blocks of the earth's crust, or during intense folding and uplift of relatively narrow zones. The latter situation is characteristic of many large mountain systems of the globe, where orogeny continues at the present time. Such mountains are called folded, although during the long history of development after the initial folding, they were also influenced by other mountain building processes.
Fold mountains.
Initially, many large mountain systems were folded, but in the course of subsequent development, their structure became very complicated. The zones of initial folding are limited by geosynclinal belts - huge troughs in which sediments accumulated, mainly in shallow oceanic settings. Before folding began, their thickness reached 15,000 m or more. The confinement of folded mountains to geosynclines seems paradoxical, however, it is likely that the same processes that contributed to the formation of geosynclines subsequently ensured the collapse of sediments into folds and the formation of mountain systems. At the final stage, folding is localized within the geosyncline, since, due to the large thickness of the sedimentary strata, the least stable zones of the earth's crust arise there.
A classic example of folded mountains is the Appalachians in eastern North America. The geosyncline in which they formed was much longer than modern mountains. For about 250 Ma, sedimentation took place in a slowly sinking basin. The maximum thickness of precipitation exceeded 7600 m. Then the geosyncline underwent lateral compression, as a result of which it narrowed to about 160 km. Sedimentary strata accumulated in the geosyncline were strongly folded and broken by faults, along which disjunctive dislocations occurred. During the stage of folding, the territory experienced intense uplift, the speed of which exceeded the rate of impact of erosion-denudation processes. Over time, these processes led to the destruction of mountains and the reduction of their surface. The Appalachians have been repeatedly uplifted and subsequently denuded. However, not all parts of the zone of initial folding experienced repeated uplift.
Primary deformations during the formation of folded mountains are usually accompanied by significant volcanic activity. Volcanic eruptions appear during folding or shortly after its completion, and large masses of molten magma pour out in folded mountains, composing batholiths. They are often exposed during deep erosional dissection of folded structures.
Many folded mountain systems are dissected by huge overthrusts with faults, along which rock covers tens and hundreds of meters thick were displaced for many kilometers. In folded mountains, both fairly simple folded structures (for example, in the Jura Mountains) and very complex ones (as in the Alps) can be represented. In some cases, the process of folding develops more intensively along the periphery of geosynclines, and as a result, transverse profile two marginal folded ridges and a central uplifted part of the mountains stand out with less development of folding. Overthrusts extend from the marginal ridges towards the central massif. Massifs of older and more stable rocks that limit the geosynclinal trough are called forelands. Such a simplified structure scheme is not always true. For example, in the mountain belt located between Central Asia and Hindustan, the sublatitudinally oriented Kunlun mountains are represented at its northern border, Himalayas - at the south, and between them the Tibetan Plateau. In relation to this mountain belt, the Tarim Basin in the north and the Hindustan Peninsula in the south are forelands.
Erosion-denudation processes in folded mountains lead to the formation of characteristic landscapes. As a result of the erosional dissection of the layers of sedimentary rocks crumpled into folds, a series of elongated ridges and valleys is formed. The ridges correspond to outcrops of more stable rocks, while the valleys are worked out in less stable rocks. Landscapes of this type are found in western Pennsylvania. With deep erosional dissection of a folded mountainous country, the sedimentary stratum can be completely destroyed, and the core, composed of igneous or metamorphic rocks, can be exposed.
Blocky mountains.
Many large mountain ranges formed as a result of tectonic uplifts that occurred along the faults of the earth's crust. The Sierra Nevada Mountains in California are a huge horn stretching approx. 640 km and a width of 80 to 120 km. The eastern edge of this horst was raised the highest, where the height of Mount Whitney reaches 418 m above sea level. The structure of this horst is dominated by granites, which form the core of a giant batholith, but sedimentary strata have also been preserved, accumulated in a geosynclinal trough in which the Sierra Nevada folded mountains were formed.
The Appalachians today are largely shaped by several processes: the original folded mountains were eroded and denuded and then uplifted along faults. However, the Appalachians cannot be considered typical blocky mountains.
A series of blocky mountain ranges lie in the Great Basin between the Rocky Mountains to the east and the Sierra Nevada to the west. These ridges were uplifted as horsts along the faults limiting them, and the final appearance was formed under the influence of erosion-denudation processes. Most of the ranges extend in the submeridional direction and have a width of 30 to 80 km. As a result of uneven uplift, some slopes turned out to be steeper than others. Long narrow valleys lie between the ridges, partially filled with sediments carried from adjacent blocky mountains. Such valleys, as a rule, are confined to subsidence zones - grabens. There is an assumption that the blocky mountains of the Great Basin were formed in the stretching zone of the earth's crust, since most of the faults here are characterized by stretching stresses.
Arch mountains.
In many areas, land areas that have experienced tectonic uplift, under the influence of erosion processes, have acquired a mountainous appearance. Where the uplift took place in a relatively small area and had an arched character, arched mountains formed, a striking example of which are the Black Hills in South Dakota, which are approx. 160 km. This area experienced arch uplift, and most of the sediment cover was removed by subsequent erosion and denudation. As a result, the central core, composed of igneous and metamorphic rocks, was exposed. It is framed by ridges composed of more resistant sedimentary rocks, while the valleys between the ridges have been worked out in less resistant rocks.
Where laccoliths (lenticular bodies of intrusive igneous rocks) have been intruded into the sedimentary rock mass, the overlying deposits could also experience dome uplifts. A good example of eroded arched uplifts is Mount Henry in Utah.
The Lake District in the west of England also experienced an arch uplift, but of somewhat lesser amplitude than in the Black Hills.
Remaining plateaus.
Due to the action of erosion-denudation processes, mountain landscapes are formed on the site of any elevated territory. The degree of their severity depends on the initial height. With the destruction of high plateaus, such as Colorado (in the southwestern United States), a highly dissected mountainous relief. The Colorado Plateau, hundreds of kilometers wide, was uplifted to a height of approx. 3000 m. Erosion-denudation processes have not yet managed to completely transform it into a mountain landscape, however, within some large canyons, for example grand canyon R. Colorado, mountains a few hundred meters high arose. These are erosional remnants that have not yet been denuded. As further development erosion processes, the plateau will acquire an increasingly pronounced mountainous appearance.
In the absence of repeated uplifts, any area will eventually level out and turn into a low monotonous plain. Nevertheless, even there, isolated hills, composed of more stable rocks, will remain. Such remnants are called monadnocks after the name of Mount Monadnock in New Hampshire (USA).
volcanic mountains
are of different types. Volcanic cones, common in almost all regions of the globe, are formed by accumulations of lava and rock fragments erupted through long cylindrical vents by forces acting deep in the bowels of the Earth. Illustrative examples of volcanic cones are Mayon Mountains in the Philippines, Mount Fuji in Japan, Popocatepetl in Mexico, Misty in Peru, Shasta in California, etc. Ash cones have a similar structure, but are not so high and are composed mainly of volcanic slag - porous volcanic rock, outwardly like ashes. Such cones are found near Lassen Peak in California and northeastern New Mexico.
Shield volcanoes are formed by repeated outpourings of lava. They are usually not as tall and not as symmetrical as volcanic cones. A lot of shield volcanoes in the Hawaiian and Aleutian Islands. In some areas, the centers of volcanic eruptions were so close together that the igneous rocks formed entire ridges that connected the originally isolated volcanoes. This type includes the Absaroka Range in the eastern part of Yellowstone Park in Wyoming.
Chains of volcanoes meet in long narrow zones. Probably the most famous example is the chain of volcanic Hawaiian Islands, stretching over 1600 km. All these islands were formed as a result of outpourings of lava and eruptions of detrital material from craters located on the ocean floor. If we count from the surface of this bottom, where the depths are approx. 5500 m, then some of the peaks of the Hawaiian Islands will be among the highest mountains in the world.
Thick layers of volcanic deposits can be cut by rivers or glaciers and turn into isolated mountains or groups of mountains. A typical example is the San Juan Mountains in Colorado. Intense volcanic activity here manifested itself during the formation of the Rocky Mountains. Lavas of various types and volcanic breccias in this area cover an area of more than 15.5 thousand square meters. km, and the maximum thickness of volcanic deposits exceeds 1830 m. Under the influence of glacial and water erosion, the massifs of volcanic rocks were deeply dissected and turned into high mountains. Volcanic rocks are currently preserved only on the tops of the mountains. Below, thick strata of sedimentary and metamorphic rocks are exposed. Mountains of this type are found on eroded areas of lava plateaus, in particular the Columbian, located between the Rocky and Cascade Mountains.
Distribution and age of mountains.
Mountains are found on all continents and many major islands- in Greenland, Madagascar, Taiwan, New Zealand, British and others. The mountains of Antarctica are largely buried under the ice sheet, but there are individual volcanic mountains, such as Mount Erebus, and mountain ranges, including the mountains of Queen Maud Land and The land of Mary Byrd is high and well-defined in relief. Australia has fewer mountains than any other continent. In North and South America, Europe, Asia and Africa, cordillera, mountain systems, ranges, mountain groups and single mountains are represented. The Himalayas, located in the south of Central Asia, are the highest and youngest mountain system in the world. The longest mountain system is the Andes in South America, stretching for 7560 km from Cape Horn to caribbean. They are older than the Himalayas and apparently had more complex history development. The mountains of Brazil are lower and much older than the Andes.
In North America, the mountains show a very wide variety in age, structure, structure, origin and degree of dissection. The Laurentian Upland, which occupies the territory from Lake Superior to Nova Scotia, is a relic of highly eroded high mountains formed in the Archaean more than 570 million years ago. In many places, only the structural roots of these ancient mountains remain. The Appalachians are intermediate in age. They first experienced uplift in the Late Paleozoic c. 280 million years ago and were much higher than now. Then they underwent significant destruction, and in the Paleogene ca. 60 million years ago were re-raised to modern heights. The Sierra Nevada mountains are younger than the Appalachians. They also went through a stage of significant destruction and re-uplift. The Rocky Mountains of the United States and Canada are younger than the Sierra Nevada but older than the Himalayas. The Rocky Mountains formed during the Late Cretaceous and Paleogene. They survived two major stages of uplift, the last being in the Pliocene, only 2–3 million years ago. It is unlikely that the Rocky Mountains have ever been higher than at present. The Cascade Mountains and Coast Ranges of the western United States and most of the mountains of Alaska are younger than the Rocky Mountains. The coast ranges of California are still experiencing very slow uplift.
Variety of structure and structure of mountains.
The mountains are very diverse not only in age, but also in structure. The Alps in Europe have the most complex structure. The rock strata there were exposed to unusually powerful forces, which was reflected in the intrusion of large batholiths of igneous rocks and in the formation of extremely diverse overturned folds and faults with huge amplitudes of displacement. In contrast, the Black Hills have a very simple structure.
The geological structure of mountains is as diverse as their structures. For example, the rocks that make up Northern part Rocky Mountains in the provinces of Alberta and British Columbia are mostly Paleozoic limestones and shales. In Wyoming and Colorado, most of the mountains have cores of granites and other ancient igneous rocks overlain by layers of Paleozoic and Mesozoic sedimentary rocks. In addition, various volcanic rocks are widely represented in the central and southern parts of the Rocky Mountains, but there are practically no volcanic rocks in the north of these mountains. Such differences are found in other mountains of the world.
Although in principle no two mountains are exactly the same, young volcanic mountains are often very similar in size and shape, as evidenced by the examples of Fujiyama in Japan and Mayon in the Philippines, which have regular cone-shaped shapes. However, note that many volcanoes in Japan are composed of andesites (an igneous rock of intermediate composition), while the volcanic mountains in the Philippines are composed of basalts (a heavier black rock containing a lot of iron). The volcanoes of the Cascades in Oregon are mostly composed of rhyolite (a rock containing more silica and less iron than basalts and andesites).
ORIGIN OF MOUNTAINS
No one can explain with certainty how mountains formed, but the lack of reliable knowledge about orogeny (mountain building) should not and does not prevent scientists from trying to explain this process. The main hypotheses for the formation of mountains are discussed below.
Submergence of ocean trenches.
This hypothesis proceeded from the fact that many mountain ranges are confined to the periphery of the continents. The rocks that make up the bottom of the oceans are somewhat heavier than the rocks that lie at the base of the continents. When large-scale movements occur in the bowels of the Earth, oceanic depressions tend to sink, squeezing the continents upward, and folded mountains form at the edges of the continents. This hypothesis not only does not explain, but also does not recognize the existence of geosynclinal troughs (depressions of the earth's crust) at the stage preceding mountain building. It does not explain the origin of such mountain systems as the Rocky Mountains or the Himalayas, which are removed from the continental margins.
Kober's hypothesis.
The Austrian scientist Leopold Kober studied the geological structure of the Alps in detail. Developing his concept of mountain building, he tried to explain the origin of large thrusts, or tectonic sheets, which are found both in the northern and southern parts of the Alps. They are composed of thick layers of sedimentary rocks subjected to significant lateral pressure, which resulted in the formation of recumbent or overturned folds. In some places, boreholes in the mountains open up the same layers of sedimentary rocks three times or more. To explain the formation of overturned folds and the associated thrusts, Kober suggested that once the central and southern parts of Europe were occupied by a huge geosyncline. Thick strata of Early Paleozoic deposits accumulated in it under the conditions of an epicontinental marine basin that filled the geosynclinal trough. Northern Europe and Northern Africa were forelands composed of very stable rocks. When the orogeny began, these forelands began to approach each other, squeezing up the unstable young sediments. With the development of this process, which was likened to a slowly compressing vise, the uplifted sedimentary rocks were crushed, formed overturned folds, or advanced on the approaching forelands. Kober tried (without much success) to apply these ideas to explain the development of other mountainous areas. In itself, the idea of lateral movement of land masses seems to explain the orogeny of the Alps quite satisfactorily, but turned out to be inapplicable to other mountains and therefore was rejected as a whole.
Continental drift hypothesis
proceeds from the fact that most mountains are located on the continental margins, and the continents themselves are constantly moving in a horizontal direction (drifting). During this drift, mountains are formed on the outskirts of the impending mainland. So, the Andes were formed during the migration South America to the west, and the Atlas Mountains - as a result of the movement of Africa to the north.
In connection with the interpretation of mountain building, this hypothesis encounters many objections. It does not explain the formation of the broad symmetrical folds that are found in the Appalachians and Jura. In addition, on its basis it is impossible to substantiate the existence of a geosynclinal trough that preceded mountain building, as well as the presence of such generally recognized stages of orogeny as the replacement of the initial folding by the development of vertical faults and the resumption of uplift. However, in last years much evidence has been found for the continental drift hypothesis, and it has gained many supporters.
Hypotheses of convection (subcrustal) currents.
For more than a hundred years, the development of hypotheses about the possibility of the existence of convection currents in the bowels of the Earth, causing deformations of the earth's surface, continued. From 1933 to 1938 alone, at least six hypotheses were put forward about the participation of convection currents in mountain building. However, all of them are based on such unknown parameters as the temperature of the earth's interior, fluidity, viscosity, crystal structure of rocks, compressive strength of various rocks, etc.
As an example, consider the Griggs hypothesis. It assumes that the Earth is divided into convection cells extending from the base of the earth's crust to the outer core, located at a depth of approx. 2900 km below sea level. These cells are the size of the mainland, but usually the diameter of their outer surface is from 7700 to 9700 km. At the beginning of the convection cycle, the masses of rocks enveloping the core are strongly heated, while on the surface of the cell they are relatively cold. If the amount of heat coming from the earth's core to the base of the cell exceeds the amount of heat that can pass through the cell, a convection current occurs. As the heated rocks rise up, the cold rocks from the surface of the cell sink. According to estimates, in order for the substance from the surface of the nucleus to reach the surface of the convection cell, it takes approx. 30 million years. During this time, long downward movements occur in the earth's crust along the cell periphery. The subsidence of geosynclines is accompanied by the accumulation of sediments hundreds of meters thick. In general, the stage of subsidence and filling of geosynclines lasts approx. 25 million years. Under the influence of lateral compression along the edges of the geosynclinal trough caused by convection currents, the deposits of the weakened zone of the geosyncline are crushed into folds and complicated by faults. These deformations occur without significant uplift of the folded strata disturbed by faults over a period of approximately 5–10 Ma. When the convection currents finally die out, the compressive forces are weakened, the subsidence slows down, and the thickness of the sedimentary rocks that filled the geosyncline rises. The estimated duration of this final stage of mountain building is approx. 25 million years.
The Griggs hypothesis explains the origin of geosynclines and their filling with sediments. It also reinforces the opinion of many geologists that the formation of folds and thrusts in many mountain systems proceeded without significant uplift, which occurred later. However, it leaves a number of questions unanswered. Do convection currents really exist? Earthquake seismograms testify to the relative homogeneity of the mantle - the layer located between the earth's crust and core. Is the division of the Earth's interior into convection cells justified? If there are convection currents and cells, mountains must appear simultaneously along the boundaries of each cell. How true is this?
The Rocky Mountain system in Canada and the United States is about the same age throughout its entire length. Its uplift began in the Late Cretaceous and continued intermittently during the Paleogene and Neogene, however, the mountains in Canada are confined to the geosyncline, which began to sag in the Cambrian, while the mountains in Colorado belong to the geosyncline, which began to form only in the Early Cretaceous. How does the hypothesis of convection currents explain such a discrepancy in the age of geosynclines, which exceeds 300 million years?
Hypothesis of swelling, or geotumor.
The heat released during the decay of radioactive substances has long attracted the attention of scientists interested in the processes occurring in the bowels of the Earth. The release of enormous amounts of heat from the explosion of the atomic bombs dropped on Japan in 1945 stimulated the study of radioactive substances and their possible role in mountain building processes. As a result of these studies, J.L. Rich's hypothesis appeared. Rich assumed that somehow large amounts of radioactive substances were concentrated locally in the earth's crust. When they decay, heat is released, under the influence of which the surrounding rocks melt and expand, which leads to swelling of the earth's crust (geotumor). When land rises between the geotumor zone and the surrounding area unaffected by endogenous processes, geosynclines form. Sediments accumulate in them, and the troughs themselves deepen both because of the ongoing geotumor and under the weight of sediments. The thickness and strength of rocks in the upper part of the earth's crust in the area of the geotumor decreases. Finally, the earth's crust in the geotumor zone turns out to be so highly elevated that part of its crust slides along steep surfaces, forming overthrusts, crushing sedimentary rocks into folds and uplifting them in the form of mountains. This kind of movement can be repeated until the magma begins to pour out from under the crust in the form of huge lava flows. When they cool, the dome settles, and the period of orogeny ends.
The swelling hypothesis has not been widely accepted. None of the known geological processes makes it possible to explain how the accumulation of masses of radioactive materials can lead to the formation of geotumors with a length of 3200–4800 km and a width of several hundred kilometers, i.e. comparable to the Appalachian and Rocky Mountain systems. Seismic data obtained in all regions of the globe do not confirm the presence of such large geotumors of molten rock in the earth's crust.
Contraction, or compression of the Earth, hypothesis
is based on the assumption that throughout the history of the existence of the Earth as a separate planet, its volume has been constantly reduced due to compression. Compression of the inner part of the planet is accompanied by changes in the solid earth's crust. Stresses accumulate discontinuously and lead to the development of powerful lateral compression and crustal deformations. Downward movements lead to the formation of geosynclines, which can be flooded by epicontinental seas and then filled with sediments. Thus, at the final stage of development and filling of the geosyncline, a long, relatively narrow wedge-shaped geological body is created from young unstable rocks, resting on the weakened base of the geosyncline and bordered by older and much more stable rocks. With the resumption of lateral compression in this weakened zone, folded mountains are formed, complicated by overthrusts.
This hypothesis seems to explain both the contraction of the earth's crust, expressed in many folded mountain systems, and the reason for the emergence of mountains at the site of ancient geosynclines. Since in many cases compression occurs deep within the Earth, the hypothesis also provides an explanation for the volcanic activity that often accompanies mountain building. However, a number of geologists reject this hypothesis on the grounds that heat loss and subsequent compression were not large enough to allow for the formation of folds and faults that are found in modern and ancient mountainous regions of the world. Another objection to this hypothesis is the assumption that the Earth does not lose, but accumulates heat. If this is true, then the value of the hypothesis is reduced to zero. Further, if the core and mantle of the Earth contain a significant amount of radioactive substances that emit more heat than can be removed, then, respectively, both the core and the mantle expand. As a result, tensile stresses will arise in the earth's crust, and by no means compression, and the entire Earth will turn into a hot melt of rocks.
MOUNTAINS AS A HUMAN HABITAT
Influence of altitude on climate.
Consider some climatic features mountain territories. Temperatures in the mountains drop by about 0.6°C for every 100 m of elevation. The disappearance of vegetation cover and the deterioration of living conditions high in the mountains are explained by such a rapid drop in temperature.
Atmospheric pressure decreases with altitude. Normal atmospheric pressure at sea level is 1034 g/cm2. At an altitude of 8800 m, which roughly corresponds to the height of Chomolungma (Everest), the pressure drops to 668 g/cm 2 . At higher altitudes large quantity heat from direct solar radiation reaches the surface, since the layer of air that reflects and absorbs radiation is thinner there. However, this layer retains less heat reflected by the earth's surface into the atmosphere. These heat losses account for the low temperatures in high altitudes Oh. Cold winds, cloudiness and hurricanes also contribute to lower temperatures. Low atmospheric pressure at high altitudes has a different effect on living conditions in the mountains. The boiling point of water at sea level is 100° C, and at an altitude of 4300 m above sea level, due to lower pressure, it is only 86° C.
The upper border of the forest and the snow line.
In descriptions of mountains, two terms are often used: "upper border of the forest" and "snow line". The upper limit of the forest is the level above which trees do not grow or hardly grow. Its position depends on average annual temperatures, precipitation, slope exposure and geographic latitude. In general, the forest boundary in low latitudes is located higher than in high latitudes. In the Rocky Mountains in Colorado and Wyoming, it passes at altitudes of 3400–3500 m, Alberta and British Columbia- drops to 2700–2900 m, and in Alaska it is even lower. Above the forest line in conditions low temperatures and sparse vegetation is inhabited by quite a few people. Small groups of nomads move across northern Tibet, and only a few Indian tribes live in the high uplands of Ecuador and Peru. In the Andes, in the territories of Bolivia, Chile and Peru, pastures are higher, i.e. at altitudes over 4000 m, there are rich deposits of copper, gold, tin, tungsten and many other metals. All foodstuffs and everything necessary for the construction of settlements and the development of deposits have to be imported from the lower regions.
The snow line is the level below which snow does not remain on the surface all year round. The position of this line varies with annual solid precipitation, slope exposure, altitude and latitude. At the equator in Ecuador, the snow line runs at an altitude of approx. 5500 m. In Antarctica, Greenland and Alaska, it is only a few meters above sea level. In the Rocky Mountains of Colorado, the height of the snow line is approximately 3700 m. This does not mean at all that snowfields are widespread everywhere above this level, but they are not below. In fact, snowfields often occupy protected areas above 3700 m, but they can also be found at lower altitudes in deep gorges and on the slopes of the northern exposure. Since snowfields, growing every year, may eventually become a source of food for glaciers, the position of the snow line in the mountains is of interest to geologists and glaciologists. In many regions of the world, where regular observations of the position of the snow line were carried out at meteorological stations, it was found that in the first half of the 20th century. its level increased, and, accordingly, the size of snowfields and glaciers decreased. There is now indisputable evidence that this trend has been reversed. It is difficult to judge how stable it is, but if it persists for many years, it could lead to the development of an extensive Pleistocene-like glaciation that ended ca. 10,000 years ago.
In general, the amount of liquid and solid precipitation in the mountains is much greater than in the adjacent plains. This can be both a favorable and a negative factor for the inhabitants of the mountains. Atmospheric precipitation can fully meet the needs for water for domestic and industrial needs, but in case of excess it can lead to devastating floods, and heavy snowfalls can completely isolate mountain settlements for several days or even weeks. Strong winds form snowdrifts that block roads and railways.
Mountains as barriers.
The mountains of the whole world have long served as barriers to communication and some activities. The only route from Central Asia to South Asia for centuries ran through the Khyber Pass on the border of modern Afghanistan and Pakistan. Countless caravans of camels and foot porters with heavy loads of goods crossed this wild place in the mountains. Famous passes in the Alps, such as St. Gotthard and Simplon, were used for many years as a connection between Italy and Switzerland. Today, through the tunnels laid under the passes, intensive railway traffic is maintained all year round. In winter, when the passes are littered with snow, everyone transport connection carried out through tunnels.
Roads.
Due to the high altitudes and rugged terrain, the construction of automobile and railways in the mountains it is much more expensive than in the plains. Automotive and railway transport it wears out faster there, and the rails under the same load fail for more short term than on the plains. Where the bottom of the valley is wide enough, the railroad track is usually placed along the rivers. However, mountain rivers often overflow their banks and can destroy large sections of roads and railways. If the width of the bottom of the valley is insufficient, the roadbed has to be laid along the sides of the valley.
Human activities in the mountains.
In the Rocky Mountains, in connection with the laying of roads and the provision of modern amenities (for example, the use of butane for lighting and heating houses, etc.), human living conditions at altitudes up to 3050 m are steadily improving. Here, in many settlements located at altitudes from 2150 to 2750 m, the number of summer houses significantly exceeds the number of houses of permanent residents.
The mountains are a relief from the summer heat. A good example of such a refuge is the city of Baguio, the summer capital of the Philippines, which was called the "city on a thousand hills." It is located just 209 km north of Manila at an altitude of approx. 1460 m. At the beginning of the 20th century. the Philippine government built government buildings, housing for employees and a hospital there, since in Manila itself it was difficult to establish an efficient operation of the government apparatus in the summer due to intense heat and high humidity. The experiment of creating a summer capital in Baguio proved to be very successful.
Agriculture.
In general, such features of the relief as steep slopes and narrow valleys limit the possibilities for the development of agriculture in the mountains of the temperate zone of North America. There, small farms mainly grow corn, beans, barley, potatoes and tobacco in some places, as well as apples, pears, peaches, cherries and berry bushes. in very warm climatic conditions bananas, figs, coffee, olives, almonds and pecans are added to this list. In the north of the temperate zone of the Northern Hemisphere and in the south of the southern temperate zone, the growing season is too short for most crops to mature, and late spring and early autumn frosts are common.
Pasture animal husbandry is widespread in the mountains. Where summer rainfall is plentiful, herbs grow well. IN Swiss Alps in summer, whole families move with their small herds of cows or goats to the high valleys, where they make cheese and make butter. In the Rocky Mountains of the United States, large herds of cows and sheep are driven from the plains to the mountains every summer, where they fatten their weight in rich meadows.
Logging
- one of the most important sectors of the economy in the mountainous regions of the globe, which ranks second after pasture animal husbandry. Some mountains are devoid of vegetation due to lack of rainfall, but in the temperate and tropical regions, most mountains are (or used to be) heavily forested. The variety of tree species is very large. Tropical mountain forests provide valuable hardwood (red, rose and ebony, teak).
Mining industry.
The extraction of metal ores is an important branch of the economy in many mountainous regions. Thanks to the development of copper, tin and tungsten deposits in Chile, Peru and Bolivia, mining settlements arose at altitudes of 3700–4600 m, where, due to the cold, strong winds and hurricanes create the most difficult living conditions. The productivity of miners there is very low, and the cost of mining products is excessively high.
Population density.
Due to the climate and topography mountainous areas often cannot be as densely populated as the plains. So, for example, in the mountainous country of Bhutan, located in the Himalayas, the population density is 39 people per 1 sq. km. km, while at a short distance from it on the low Bengal plain in Bangladesh, it is more than 900 people per 1 sq. km. km. Similar differences in population density in the mountains and on the plains exist in Scotland.
| MOUNTAIN PEAKS | |||
| Absolute height, m | Absolute height, m | ||
| EUROPE | NORTH AMERICA | ||
| Elbrus, Russia | 5642 | McKinley, Alaska | 6194 |
| Dykhtau, Russia | 5203 | Logan, Canada | 5959 |
| Kazbek, Russia - Georgia | 5033 | Orizaba, Mexico | 5610 |
| Mont Blanc, France | 4807 | St. Elias, Alaska - Canada | 5489 |
| Ushba, Georgia | 4695 | Popocatepetl, Mexico | 5452 |
| Dufour, Switzerland - Italy | 4634 | Foraker, Alaska | 5304 |
| Weishorn, Switzerland | 4506 | Iztaxihuatl, Mexico | 5286 |
| Matterhorn, Switzerland | 4478 | Lucaynia, Canada | 5226 |
| Bazarduzu, Russia - Azerbaijan | 4466 | Bona, Alaska | 5005 |
| Finsterarhorn, Switzerland | 4274 | Blackburn, Alaska | 4996 |
| Jungfrau, Switzerland | 4158 | Sanford, Alaska | 4949 |
| Dombay-Ulgen (Dombay-Elgen), Russia - Georgia | 4046 | Wood, Canada | 4842 |
| Vancouver, Alaska | 4785 | ||
| ASIA | Churchill, Alaska | 4766 | |
| Chomolungma (Everest), China - Nepal | 8848 | Fairweather, Alaska | 4663 |
| Chogori (K-2, Godwin Austen), China | 8611 | Baer, Alaska | 4520 |
| Hunter, Alaska | 4444 | ||
| Kanchenjunga, Nepal - India | 8598 | Whitney, California | 4418 |
| Lhotse, Nepal - China | 8501 | Elbert, Colorado | 4399 |
| Makalu, China - Nepal | 8481 | Massif, Colorado | 4396 |
| Dhaulagiri, Nepal | 8172 | Harvard, Colorado | 4395 |
| Manaslu, Nepal | 8156 | Rainier, Washington | 4392 |
| Chopu, China | 8153 | Nevado de Toluca, Mexico | 4392 |
| Nanga Parbat, Kashmir | 8126 | Williamson, California | 4381 |
| Annapurna, Nepal | 8078 | Blanca Peak, Colorado | 4372 |
| Gasherbrum, Kashmir | 8068 | La Plata, Colorado | 4370 |
| Shishabangma, China | 8012 | Ancompagre Peak, Colorado | 4361 |
| Nandadevi, India | 7817 | Creston Peak, Colorado | 4357 |
| Rakaposhi, Kashmir | 7788 | Lincoln, Colorado | 4354 |
| Kamet, India | 7756 | Grace Peak, Colorado | 4349 |
| Namchabarwa, China | 7756 | Antero, Colorado | 4349 |
| Gurla Mandhata, China | 7728 | Evans, Colorado | 4348 |
| Ulugmuztag, China | 7723 | Longs Peak, Colorado | 4345 |
| Kongur, China | 7719 | White Mountain Peak, California | 4342 |
| Tirichmir, Pakistan | 7690 | North Palisade, California | 4341 |
| Gungashan (Minyak Gankar), China | 7556 | Wrangel, Alaska | 4317 |
| Kula Kangri, China - Bhutan | 7554 | Shasta, California | 4317 |
| Muztagata, China | 7546 | Sill, California | 4317 |
| Communism Peak, Tajikistan | 7495 | Pikes Peak, Colorado | 4301 |
| Victory Peak, Kyrgyzstan - China | 7439 | Russell, California | 4293 |
| Jomolhari, Bhutan | 7314 | Split Mountain, California | 4285 |
| Lenin Peak, Tajikistan - Kyrgyzstan | 7134 | Middle Palisade, California | 4279 |
| Korzhenevskiy peak, Tajikistan | 7105 | SOUTH AMERICA | |
| Khan Tengri Peak, Kyrgyzstan | 6995 | Aconcagua, Argentina | 6959 |
| Kangrinboche (Kailash), China | 6714 | Ojos del Salado, Argentina | 6893 |
| Khakaborazi, Myanmar | 5881 | Bonet, Argentina | 6872 |
| Damavend, Iran | 5604 | Bonete Chico, Argentina | 6850 |
| Bogdo-Ula, China | 5445 | Mercedario, Argentina | 6770 |
| Ararat, Türkiye | 5137 | Huascaran, Peru | 6746 |
| Jaya, Indonesia | 5030 | Llullaillaco, Argentina - Chile | 6739 |
| Mandala, Indonesia | 4760 | Erupaha, Peru | 6634 |
| Klyuchevskaya Sopka, Russia | 4750 | Galan, Argentina | 6600 |
| Trikora, Indonesia | 4750 | Tupungato, Argentina - Chile | 6570 |
| Belukha, Russia | 4506 | Sajama, Bolivia | 6542 |
| Munkhe-Khairkhan-Uul, Mongolia | 4362 | Coropuna, Peru | 6425 |
| AFRICA | Illampu, Bolivia | 6421 | |
| Kilimanjaro, Tanzania | 5895 | Illimani, Bolivia | 6322 |
| Kenya, Kenya | 5199 | Las Tortolas, Argentina - Chile | 6320 |
| Rwenzori, Congo (DRC) – Uganda | 5109 | Chimborazo, Ecuador | 6310 |
| Ras Dashen, Ethiopia | 4620 | Belgrano, Argentina | 6250 |
| Elgon, Kenya - Uganda | 4321 | Toroni, Bolivia | 5982 |
| Toubkal, Morocco | 4165 | Tutupaca, Chile | 5980 |
| Cameroon, Cameroon | 4100 | San Pedro, Chile | 5974 |
| AUSTRALIA AND OCEANIA | ANTARCTICA | ||
| Wilhelm, Papua New Guinea | 4509 | Vinson array | 5140 |
| Giluwe, Papua New Guinea | 4368 | Kirkpatrick | 4528 |
| Mauna Kea, about. Hawaii | 4205 | markham | 4351 |
| Mauna Loa, about. Hawaii | 4169 | Jackson | 4191 |
| Victoria, Papua New Guinea | 4035 | Sidley | 4181 |
| Capella, Papua New Guinea | 3993 | Minto | 4163 |
| Albert Edward, Papua New Guinea | 3990 | Wörtherkaka | 3630 |
| Kosciuszko, Australia | 2228 | Menzies | 3313 |
163 0
blocky mountains are formed as a result of breaking rock masses into separate blocks (blocks) and raising them to different heights. As a rule, they arise where rocks have lost their plasticity (consolidated) as a result of a long and complex development and, under the influence of endogenous forces, behave like a fragile body, splitting into blocks. Faults separating blocks can be deep. from 1–3 km to several tens of kilometers, they can be vertical (faults) or inclined (thrusts). In the relief, faults are expressed either as ledges or as linear valleys developed by erosion. often have relatively flat, horizontal or slightly inclined tops, which are the undisturbed surface of raised blocks; they are characterized by steep slopes and relatively rare dissection. If the raised blocks as a whole form a gently convex shape, such mountains are called arched-blocky. An example of blocky mountains is the Sierra Nevada mountains in the west. America, the system of ridges North. Tien Shan.
Meanings in other dictionaries
Deep
Old City in Belarus (see Belarus), district center Vitebsk region (see Vitebsk region); known in written sources since the 16th century. Railroad station. Food industry. The population is 17.5 thousand people (2004). The city is picturesquely spread between two majestic lakes. In the 17-18 centuries. on the main square (September 17 Square) two monumental baroque churches were built, facing...
Glukhov
Hlukhiv, city in Sumy region (Ukraine), 115 km to the NW. from Sumy. 36 thousand inhabitants (1996). As the city has been known since 1152. It was the center of grain trade and sugar. prom. Anastasevsky Cathedral, Kyiv Triumphal Gates (1766), Gamaleevsky Monastery; churches (XVII-XVIII centuries) - Nikolaevskaya, Spaso-Preobrazhenskaya, Voznesenskaya. Pedagogical institute (1874); Research Institute of Bast Crops. Museums: local history and p...
Glaciology
glaciology is the science of natural systems whose properties and dynamics are determined by ice. The subject of its study are natural ice on the Earth's surface, in the atmosphere, hydrosphere and lithosphere - the regime and dynamics of their development, interaction with the environment, the role of ice in the evolution of the Earth. United natural object studies of glaciology are the glaciosphere and its constituent nival-glacial systems ...
The mountains differ not only in their height, variety of landscape, size, but also in their origin. There are three main types of mountains: blocky, folded and domed mountains.
How are rocky mountains formed?
The earth's crust does not stand still, but is in constant motion. When cracks or faults of tectonic plates appear in it, huge masses of rock begin to move not in the longitudinal, but in the vertical direction. Part of the rock can then fall through, and the other part, adjacent to the fault, rise. An example of the formation of blocky mountains is the Teton mountain range. This range is located in Wyoming. On the eastern side of the ridge, sheer rocks are visible, which rose when the earth's crust was broken. On the other side of the Teton Ridge is a valley that sank down.
How are folded mountains formed?
The parallel movement of the earth's crust leads to the appearance of folded mountains. The appearance of folded mountains is best seen in the example of the famous Alps. The Alps arose as a result of the collision of the lithospheric plate of the continent of Africa and the lithospheric plate of the continent of Eurasia. For several million years, these plates have been in contact with each other with tremendous pressure. As a result, the edges of the lithospheric plates were crumpled, forming giant folds, which eventually became covered with faults. Thus, one of the most majestic mountain ranges in the world was formed.
How are domed mountains formed?
Inside the earth's crust is hot magma. Magma, breaking upwards under enormous pressure, lifts the rocks that lie above. Thus, a dome-shaped bending of the earth's crust is obtained. Over time, wind erosion exposes igneous rock. An example of domed mountains is dragon mountains located in South Africa. More than a thousand meters high, weathered igneous rock is clearly visible in it.
blocky mountains
Blocky mountains
are formed as a result of breaking rock strata into separate blocks (blocks) and raising them to different heights. As a rule, they arise where rocks have lost their plasticity (consolidated) as a result of a long and complex development and, under the influence of endogenous forces, behave like a fragile body, splitting into blocks. Faults separating blocks can be deep. from 1–3 km to several tens of kilometers, they can be vertical (faults) or inclined (thrusts). In the relief, faults are expressed either as ledges or as linear valleys developed by erosion. Blocky mountains often have relatively flat, horizontal or slightly inclined peaks, which are an undisturbed surface of uplifted blocks; they are characterized by steep slopes and relatively rare dissection. If the raised blocks as a whole form a gently convex shape, such mountains are called arch-block. An example of blocky mountains is the Sierra Nevada mountains in the west. America, the system of ridges North. Tien Shan.
Geography. Modern illustrated encyclopedia. - M.: Rosman. Under the editorship of prof. A. P. Gorkina. 2006 .
See what "blocky mountains" are in other dictionaries:
blocky mountains- Mountains formed by multidirectional movements of the earth's crust blocks along the faults. Syn.: fault mountains… Geography Dictionary
blocky mountains- — Topics oil and gas industry EN block type of mountain … Technical Translator's Handbook
Uplifts of the earth's crust, limited by tectonic faults. Gypsies are characterized by massiveness, steep slopes, and comparatively weak dissection. They usually occur in folded zones that once had a mountainous terrain, but have lost ... ...
fold-block mountains- Mountains formed under the combined action of folded and blocky tectonic processes ... Geography Dictionary
Mountains formed by folded rock strata, broken along the lines of young faults into blocks raised to different heights. Usually they are so-called. revived mountains formed within epiplatform orogenic belts ... ... Great Soviet Encyclopedia
A set of closely spaced individual mountains, mountain ranges, mountain spurs, ridges, highlands, as well as canyons, valleys, depressions separating them, occupying a certain territory, more or less clearly separated from the surrounding plains. By… … Geographic Encyclopedia
1. in Greek mythology Ora, in Greek mythology, the goddess of nature and the seasons. Usually there were three of them, and they personified spring, summer and winter. They were portrayed as young and beautiful maidens, accompanied by nymphs and graces (charites). According to… … Collier Encyclopedia
Formed by blocks of the earth's crust, lifted and moved relative to each other. There are mountains formed by: a) blocks composed of horizontally occurring settlements, and b) previously folded structures, later peneplanated and ... ... Geological Encyclopedia
Formed by the latest tekt. movements in place of platforms of different ages, ch. arr. in place of the protrusions of the foundation in the form of shields (basement plains). P. are composed, usually metamorphosed to one degree or another, sometimes crystalline, crumpled into ... ... Geological Encyclopedia
Not to be confused with mountains as isolated sharp rises of rock, as well as peaks in mountainous countries. Mountains are highly dissected parts of the land, significantly, by 500 meters or more, elevated above the adjacent plains. From the plains of the mountain ... ... Wikipedia
Mountains occupy about 24% of all land. Most mountains in Asia - 64%, least of all in Africa - 3%. 10% of the world's population lives in mountains. And it is in the mountains that most of the rivers on our planet originate.
Characteristics of the mountains
By geographical location, mountains are combined into various communities, which should be distinguished.
. mountain belts- the largest formations, often stretching across several continents. For example, the Alpine-Himalayan belt runs through Europe and Asia, or the Andean-Cordillera, stretching through North and South America.
. mountain system- groups of mountains and ranges, similar in structure and age. For example, the Ural Mountains.
. mountain ranges- a group of mountains, elongated in a line (Sangre de Cristo in the USA).
. mountain groups- also a group of mountains, but not elongated in a line, but simply located nearby. For example, the Ber-Po Mountains in Montana.
. Solitary mountains- not related to others, often of volcanic origin (Table Mountain in South Africa).
Natural areas of mountains
Natural areas in the mountains are arranged in layers and change depending on the height. At the foot, there is most often a zone of meadows (in the highlands) and forests (in the middle and low mountains). The higher, the more severe the climate becomes.
The change of belts is influenced by climate, height, topography of mountains and their geographical position. For example, continental mountains do not have a belt of forests. From the foot to the top, natural areas change from deserts to grasslands.
Mountain views
There are several classifications of mountains according to various criteria: by structure, shape, origin, age, geographical location. Consider the most basic types:
1. By age distinguish old and young mountains.
old called mountain systems, whose age is hundreds of millions of years. The internal processes in them have subsided, and the external ones (wind, water) continue to destroy, gradually comparing them with the plains. The old mountains include the Ural, Scandinavian, Khibiny (on the Kola Peninsula).
2. Height distinguish between low, medium and high mountains.
Low mountains (up to 800 m) - with rounded or flat tops and gentle slopes. There are many rivers in these mountains. Examples: Northern Urals, Khibiny, spurs of the Tien Shan.
Medium mountains (800-3000 m). They are characterized by a change in landscape depending on the height. These are the Polar Urals, the Appalachians, the mountains of the Far East.
High mountains (over 3000 m). Basically, these are young mountains with steep slopes and sharp peaks. Natural areas change from forests to icy deserts. Examples: Pamir, Caucasus, Andes, Himalayas, Alps, Rocky Mountains.
3. By origin they distinguish volcanic (Fujiyama), tectonic (Altai Mountains) and denudation, or erosional (Vilyuysky, Ilimsky).
4. According to the shape of the top mountains are peak-shaped (Communism Peak, Kazbek), plateau-shaped and table-shaped (Amby in Ethiopia or Monument Valley in the USA), domed (Ayu-Dag, Mashuk).
Climate in the mountains
The mountain climate has a number characteristic features, which appear with height.
Decrease in temperature - the higher, the colder. It is no coincidence that the peaks of the highest mountains are covered with glaciers.
The atmospheric pressure drops. For example, at the top of Everest, the pressure is two times lower than at sea level. That is why water in the mountains boils faster - at 86-90ºC.
The intensity of solar radiation increases. In the mountains, sunlight contains more ultraviolet light.
The amount of precipitation is increasing.
High mountain ranges delay precipitation and affect the movement of cyclones. Therefore, the climate on different slopes of the same mountain may differ. On the windward side there is a lot of moisture, sun, on the leeward side it is always dry and cool. A striking example is the Alps, where subtropics are represented on one side of the slopes, and a temperate climate dominates on the other.
The highest mountains in the world
(Click on the picture to enlarge the scheme in full size)
There are seven highest peaks in the world, which all climbers dream of conquering. Those who succeeded become honorary members of the "Seven Peaks Club". These are mountains such as:
. Chomolungma, or Everest (8848 m). Located on the border of Nepal and Tibet. Refers to mountain system Himalayas. It has the shape of a trihedral pyramid. The first conquest of the mountain took place in 1953.
. aconcagua(6962 m). It is the highest mountain in the southern hemisphere, located in Argentina. Belongs to the Andes mountain system. The first ascent took place in 1897.
. McKinley- the highest peak in North America (6168 m). Located in Alaska. First conquered in 1913. It was considered the highest point in Russia until Alaska was sold to America.
. kilimanjaro- the highest mark in Africa (5891.8 m). Located in Tanzania. First conquered in 1889. This is the only mountain where all types of the Earth's belts are represented.
. Elbrus- the highest peak in Europe and Russia (5642 m). Located in the Caucasus. The first ascent took place in 1829.
. Vinson Massif- the highest mountain of Antarctica (4897 m). It is part of the Ellsworth Mountains. First conquered in 1966.
. Mont Blanc — highest point Europe (many attribute Elbrus to Asia). Height - 4810 m. Located on the border of France and Italy, belongs to the mountain system of the Alps. The first ascent in 1786, and a century later, in 1886, Theodore Roosevelt conquered the summit of Mont Blanc.
. Pyramid of Carstens- the highest mountain in Australia and Oceania (4884 m). Located on the island of New Guinea. The first conquest was in 1962.